Summary
This analysis covers the details of Polygon’s proposed implementation of bridged assets and its risk profile. It will also cover past events that presented similar risk profiles.
We support adjusting risk parameters for Aave V2 and V3 deployments on Polygon, specifically for the affected stablecoin markets. This action aligns with Aave’s proactive risk management strategy, which mitigates exposure to increased risks stemming from external bridge vulnerabilities. This approach has precedent in Aave governance, with successful actions to mitigate similar risks on Fantom following the Harmony bridge exploit.
Motivation
The Polygon governance proposal seeks to utilize the ~$1.3 billion in stablecoin reserves held by the Polygon PoS Portal Bridge to gradually deploy into curated liquidity pools.
The proposal outlines a phased approach for deploying stablecoin reserves (DAI, USDC.e, and USDT) into specific yield-bearing vaults. These vaults, curated by Allez Labs, Morpho Association, and Yearn, will follow different yield strategies with each asset:
- DAI: Deployed into Maker’s sUSDS, a canonical yield-bearing wrapper for the Maker ecosystem.
- USDC and USDT: Deployed into Morpho Vaults, curated by Allez Labs, which act as the core yield source. The vaults will support lending against assets like USTB (Superstate), sUSDS (Maker), and stUSD (Angle).
We consider the governance proposal to substantially alter the risk dynamics for assets in Aave’s Polygon deployments. History has shown that bridge vulnerabilities can lead to catastrophic losses in DeFi, exemplified by major exploits, including Multichain and Harmony, which directly affected Aave in the past.
Additionally, such a proposal, if passed, sets a dangerous precedent for rehypothication at the bridge level and thus exposes the users and protocols to unmanageable risk.
Harmony and Fantom
The Harmony Horizon bridge exploit led to a $100M loss, significantly impacting Aave V3 Harmony. Exploited bridged assets, including DAI, USDC.e, USDT, and AAVE, saw price discrepancies, creating arbitrage opportunities where users collateralized depreciated assets to borrow unaffected ones (ONE and LINK). This disrupted the protocol’s health factor mechanics, as positions appeared healthy despite underlying asset devaluation. In response, the DAO halted borrowing to prevent further arbitrage and stabilize the pool, although Aave suffered from the creation of $750K of bad debt.
Subsequently to the Harmony Bridge exploit, Aave proposed freezing its V3 market on Fantom. This action aimed to mitigate risks associated with the network’s dependency on the Anyswap (Multichain) bridge, successfully preventing losses from the Multichain Hack of June 2023.
Economics
The fees accrued from Aave’s Polygon instances represent only 3.8% of the protocol’s total revenue, with 2% of that coming from Polygon V2, which is already in the process of being deprecated. This leaves the remaining revenue contribution from Polygon V3 at a mere 1.8%, a negligible amount compared to the significant additional risks posed by the proposed changes. Given this minimal revenue impact, it is not justifiable to expose the protocol and the Safety Module to the risk of this proposal.
Vaults risk
To properly determine the risks introduced by the new Polygon proposal, we cover the proposed deployment of Polygon PoS Bridge stablecoins into various yield-bearing vaults. Our analysis determined that introducing the yield-bearing vaults introduces significant risks to some of the assets, particularly due to the limited liquidity of the underlying assets and the highly aggressive parameters utilized.
DAI: Managed Exposure
DAI reserves would be allocated to Maker’s sUSDS, which offers atomic withdrawals. While this structure minimizes direct risk exposure, it relies on Maker’s governance and underlying stability.
USDC and USDT: Morpho Vault Risks
USDC and USDT reserves are slated for deposit into Morpho Vaults, targeting Superstate’s USTB, Maker’s sUSDS, and Angle’s USD. This allocation raises critical liquidity concerns:
-
Superstate’s USTB
USTB represents a tokenized fund tied to U.S. Treasury Bills, but its on-chain supply is alarmingly small, with only $117M in assets under management compared to the assets currently deposited in Polygon POS Bridge, which account for $1.3B.
-
Angle’s stUSD
Angle’s stUSD relies on USDa as its backing, with USDa hardcoded to $1 in its oracle. This dependency could propagate exploits in USDA to stUSD. Notably, Angle’s agEUR stablecoin suffered a substantial loss of backing during the Euler hack, raising doubts on the resilience of assets with a similar exposure to vast smart-contract risks. Furthermore, stUSD’s current market size on Morpho is just $1M, with a total USDa supply of $27M—far too small to handle the proposed inflows.
Morpho Architecture
A critical concern with the proposed use of Morpho vaults lies in the immutability of Morpho’s parameters, which prevents risk providers from rapidly adjusting key settings, such as the UOptimal and IR curve, in response to market changes. In addition, Morpho utilizes a set of hardcoded parameters such as 90% UOptimal and a conditional time-based interest rate mechanism, which severely limits the availability of withdrawn liquidity and adaptability in the case of significant bridge outflow.
Given this architecture, Aave cannot dynamically manage risks as conditions change, leaving the protocol reliant on a third party’s fixed parameterization. Furthermore, the lack of clarity around the total exposure of assets within Morpho adds an additional layer of risk.
Recommendation
We recommend setting the LTV to 0% only for the affected assets of DAI, USDC.e, and USDT. This approach addresses the heightened risk that, in the event of a loss of funds, the affected stablecoins could trade below their oracle-reported value, enabling them to be used as collateral to borrow other assets for more than their real worth. Additionally, we will recommend gradually reducing the LT for these assets to 0 in the future in order to offboard any utilization as collateral. While this is a rare occurrence, given the affected assets are primarily stablecoins, there is currently $18.7M worth of debt against them in the Polygon V3 instance.
However, to avoid immediate and drastic outflows that could also lead to illiquidity risks and rate volatility risks, we recommend against setting the Reserve Factor to 85% and, instead, limiting the increase to 25% initially and only for USDT. This approach provides an immediate response while allowing for monitoring of the market dynamics. If the proposal proceeds, further increases in the Reserve Factor should be implemented gradually to minimize disruptions, ideally in combination with alternative parameter changes like adjusting Slope 1 or Slope 2 based on the asset specifics.
Finally, we strongly support removing Aave V3 Polygon from the Safety Module and canceling the umbrella deployment on Polygon.
Specification
Deployment |
Asset |
Current LTV |
Proposed LTV |
Current RF |
Proposed RF |
Polygon V3 |
DAI |
63% |
0% |
25% |
- |
Polygon V3 |
USDC.e |
75% |
0% |
50% |
- |
Polygon V3 |
USDT |
75% |
0% |
10% |
25% |
Polygon V2 |
USDC.e |
75% |
0% |
99.9% |
- |
Polygon V2 |
DAI |
63% |
0% |
99.9% |
- |
Disclaimer
Chaos Labs has not been compensated by any third party for publishing this ARFC.
Copyright
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